I downloaded cmake-3.18.6-Linux-x86_64.sh and ran it as ./cmake-3.18.6-Linux-x86_64.sh. I also downloaded cmake-3.18.6-Linux-x86_64.tar.gz and upacked it. Both gave me a directory that included bin/, doc/, man/ and share/ but there was no Readme.txt, no bootstrap.sh and no CMakeLists.txt.
So, does this directory tree include pre-compiled files? Where are the instructions for this? I do not want to leave the directory under ~/Downloads.